Pressure sensors serve for registering pressures and are used in industrial measurements technology, for example, for fill level measurement or for flow measurement. In such case, various kinds of pressure sensors are used, depending on area of application. Thus, a pressure sensor can be embodied, for example, as an absolute pressure sensor, as a relative pressure sensor or also as a pressure difference sensor. In principle, however, all pressure sensors are equally constructed and comprise typically a housing in which a pressure sensor element is arranged. Semiconductor pressure sensor elements are popular in pressure measuring technology, for example, pressure sensor elements based on silicon. Semiconductor pressure sensor elements include a measuring membrane, which typically has four resistance elements integrated in its edge region. The measuring membrane is supplied on its first side with a first pressure and on its second side with a second pressure, so that the two pressures bring about a deflection of the measuring membrane. The pressure-dependent deflection of the measuring membrane is registered by the integrated resistance elements and evaluated, so that a pressure measurement variable can be output. As a function of whether the pressure sensor is a relative pressure sensor, an absolute pressure sensor or a pressure difference sensor, the measuring membrane is supplied with the appropriate two pressures.
In the case, in which the pressure sensor is embodied as an absolute pressure sensor, one of the two sides of the measuring membrane is exposed to a vacuum and the other side of the measuring membrane is fed a media pressure to be measured. The absolute pressure sensor measures, thus, the absolute pressure, thus the media pressure to be measured relative to vacuum as reference pressure.
In the case, in which the pressure sensor is embodied as a relative pressure sensor, one of the two sides of the measuring membrane is exposed to atmospheric air pressure as a reference pressure and the other side of the measuring membrane is fed a media pressure to be measured. The relative pressure sensor measures, thus, a relative pressure, thus the media pressure to be measured relative to the atmospheric air pressure.
In the case, in which the pressure sensor is embodied as a pressure difference sensor, one of the two sides of the measuring membrane is fed a first media pressure to be measured and the other side of the measuring membrane a second media pressure to be measured. The pressure difference sensor measures, thus, a pressure difference, thus the difference between the two media pressures.
In ordinary measurement operation, there are always disturbances, which can be significant enough to cause such pressure sensors to fail. Along with that, such pressure sensors have the problem that they are subject to drift, for example, from deposits or aging, such that a corrupted pressure measurement variable can be ascertained.
In order to detect such unintended behavior of pressure sensors, it is necessary that they be monitored or checked during measurement operation.